1. Field of the Invention
The present invention relates to a method for fabricating a capacitor, and more particularly, to a method for fabricating a metal-insulator-metal capacitor.
2. Description of the Prior Art
Use of and interest in merged memory and logic semiconductor devices is increasing. A merged memory and logic device is a structure where a memory, such as a DRAM, and a logic, such as a logic circuit, are implemented in a single chip. Implementation of a memory and logic in a single chip in a merged memory and logic semiconductor device is advantageous over conventional chips as high-speed and low-power driving is possible without any particular change in design. Furthermore, merged memory and logic semiconductor devices may include a number of common hardware devices including capacitors.
Capacitors are elements that are used extensively in semiconductor devices for storing an electrical charge. Capacitors essentially comprise two conductive plates separated by an insulator. The capacitance, or amount of charge held by the capacitor per applied voltage, depends on a number of parameters such as the area of the plates, the distance between the plates, and the dielectric constant value of the insulator between the plates, as examples. Capacitors can be used in filters, analog-to-digital converters, memory devices, control applications, and many other types of semiconductor devices.
One type of capacitor is a metal-insulator-metal (MIM) capacitor, which is frequently used in mixed signal devices and logic semiconductor devices, as examples. MIM capacitors are used to store a charge in a variety of semiconductor devices. MIM capacitors are often used as storage nodes in a memory device, for example. A MIM capacitor is typically formed horizontally on a semiconductor wafer, with two metal plates sandwiching a dielectric layer parallel to the wafer surface. Therefore, MIM capacitors have often been referred to as thin-film capacitors. As a result, it is difficult to manufacture MIM capacitors which have a relatively large capacitance per unit area.
Furthermore, conventional MIM capacitors have low breakdown voltages and typically are not suitable to be used in high voltage applications, for example, greater than 2.5V. As a result, a need exists for embedded MIM capacitors capable of handling higher voltage applications with larger breakdown voltage tolerances.